[idea] Mutable pointee/ RCString

[Iakh via Digitalmars-d]

Is it hard to make pointee data mutable?
E.g. if have:
------
struct RCString
{
    private char[] data;
    private @mutable int* counter;
}
------
So for optimiser (in case of immutable) this looks like
------
struct RCString
{
    private char[] data;
    private @mutable void* counter; // pointer to garbage
}
------